In certain applications, such as in firefighting, there is a need to propel large quantities of a fluid or a powdered material over significant distances, with accurate control of placement and position. This can be accomplished by using a short duration gas pulse to propel the extinguishant. It is also desireable to minimize the dispersion of the propelled extinguishant. This can be accomplished by propelling the extinguishant in a highly focussed stream.
The generation of a gas pulse which is effective as a propellant for, for example, firefighting applications requires the release of a relatively large volume of gas during a relatively short duration pulse. Typically, several cubic feet of gas would be released in several hundredths of a second. Of necessity, the generation of such a pulse requires the use of compressed gas at elevated pressures substantially in excess of 100 psi. At such elevated pressures, it has proven difficult, if not impossible, to operate conventional valves rapidly enough to produce the requisite short duration pulses, because it has been necessary to overcome some portion of the high operating pressure, in order to open the valve. Also, the high-operating pressure has a tendency to damage valve components as the valve opens or closes under the influence of the relatively high pressure.
Highly focussed gas generators, called "vortex" generators, are known and have been suggested for providing the necessary propellent force for the extinguishant. Although such vortex generators have been demonstrated on an experimental basis, consistent and reliable operation has not been possible until now. The primary shortcoming has also been the unavailability of an appropriate valve for generating a highly focussed gas vortex.
Broadly, it is an object of the present invention to generate a short duration, high volume gas pulse and to provide an apparatus for doing so.
It is a specific object of the present invention to provide a gas valve capable of rapid opening and closing under high pressure, while also being capable of delivering a relatively high volume of gas during its open intervals.
It is also an object of the present invention to provide a gas valve capable of delivering a low dispersion gas flow.
It is another object of the present invention to provide a generator of a short duration , high volume gas pulse and a pulsed valve for use therein, both of which are reliable, convenient and effective in use, yet relatively inexpensive in construction.
In accordance with an illustrative embodiment demonstrating objects and features of the present invention, there is provided a fire extinguisher including a barrel and a highly-focussed, pulsed gas valve at the rear of the barrel. The barrel is charged with, typically, 20-30 pounds of extinguishant in the form of a liquid or a powder, and this charge is propelled, upon the operation of the gas valve.
In accordance with the present invention, the gas valve includes an outer chamber with an exhaust gas outlet at the front. Inside the outer chamber, there is provided an inner chamber which extends along the outer chamber and terminates, at its forward end, in an opening aligned with the exhaust gas outlet of the outer chamber. The inner chamber opening is spaced rearwardly at a distance from the exhaust gas outlet. Within the inner chamber, a piston is mounted for reciprocal movement between the front and rear of the valve, and the length of the piston is selected to be greater than the distance between the gas outlet and inner chamber opening. Between its front and rear, the piston is provided with a forwardly directed, peripheral seat. The piston is larger than the outer chamber gas outlet. Thus, when the inner chamber is filled with gas at a moderate pressure, the piston is forced forward and closes the valve outlet. The outer chamber can then be filled with a charge of gas at high pressure. In order to fire the valve, the pressure in the inner chamber is released, whereupon the high pressure acting on the peripheral rim area of the piston urges the piston rearward. When the piston uncovers the valve outlet opening, the full pressure of the outer chamber charge acts on the front of the piston, and the piston is accelerated rapidly rearwardly, to fully open the gas outlet. The gas charge of the outer chamber is therefore rapidly discharged. Thereafter, the valve is once more closed by re-pressurizing the inner chamber and the charge/discharge cycle may be repeated.
It is a feature of the present invention that a pulsed gas valve is provided which is capable of generating a highly focussed vortex gas flow.